I've noticed that too, seems REALLY recent. I picked up a 158 not long ago at the thrift shop and when I was researching it I didn't really see them going for more than $100. Now I do. (I paid $15 for mine and it's in nearly perfect shape, I got SO lucky!!) I was hoping to find another similar machine to give to a friend but not for $100+. I like to be generous but I can't be THAT generous! (And I'm not letting go of MINE! I've fallen too far in love to let it go now.)
They deserve the respect though. I'm pretty impressed with the one I have; it's not a complicated machine but it's very solid, in every meaning of the word. Maybe we should stop talking about how great they are, LOL.